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Chapter 6: Operating Principles
DATOSPIR MICRO User’s Manual 194
511-A00-MU2 • REV. 2.06
The DATOSPIR MICRO spirometer is a piece of equipment
that acquires physical signals and processes the information
provided by the signal related to the pulmonary function. For
processing purposes, physical must be changed to electrical.
The units responsible for this change are called transducers. The
DATOSPIR MICRO has a Turbine-type transducer.
The turbine transducer performs transduction in two stages: The
volume to be measured crosses the turbine and prints its rotation
that is proportional to that volume. This rotation is detected by
the interrupting of a beam of infrared light, the sensor of which
converts the light received into a digital-type electrical signal.
6.1 TURBINE
The turbine is axial with two stators in the form of a propeller and
a rotor made up of a flat, rectangular blade. The shape of the
stators means that the air flow passing turns, which makes the
blade turn. The turbine operates based on the Fluid Mechanics
theory and, more specifically, the Machine Turbo theory. Applied to
this case, the angle at which the rotor turns is directly proportional
to the fluid volume crossing the turbine and the proportionality
constant depends on its shape.
6.2 TURBINE ROTATION SENSOR
The turbine rotation sensor consists of three pairs of emitting
diodes and an infrared (invisible) photo-transistor that,
appropriately positioned, detect the rotation and its direction.
The number of times the beam is interrupted is equivalent to
an accumulated angle of rotations and, therefore, the voluem
of air to have crossed the turbine. The photo-transistor provides
a digital electrical signal that represents the times the beam of
light is interrupted and is directly acquired by the microprocessor.